: The long-term goal of this research is to understand the dynamic changes in cortical activation which underlie implicit motor learning. In the current proposal we use the serial reaction time task (SRTT) of Nissen and Bullemer as a model of implicit motor learning and study functional activation in cortical motor areas during its performance using both blocked design and event-related fMRI. The specific aims are as follows: (1) To study the neural substrate of learning in a variant of the SRTT in which subjects point to different sets of spatial targets, (2) to evaluate the functional correlates of an impairment in implicit learning which occurs under isometric conditions, (3) to determine the neural substrate of performance-based implicit learning in conditions in which the expression of learning is manipulated by varying the rate of stimulus presentation, and (4) to examine activation in cortical motor areas during learning in the SRTT using event-related fMRI. The data collected for each of the aims will enable us to address the following issues: (i) Which aspect of the motor behavior is encoded and what is its neural substrate, (ii) What is the role of proprioceptive feedback in implicit learning, and does the way in which it modulates functional activation inform us about the learning process itself, (iii) Will the dissociation we have observed between learning and performance be reflected in the differential activation of motor areas important for the translation of knowledge into action, and (iv) to what extent is learning reflected in changes in the relative timing of activation among cortical motor areas. As much of our motor behavior is based on implicit learning it is possible that implicit learning paradigms could be used beneficially for motor rehabilitation in stroke.